<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
      *{margin: 0;padding: 0}
      #wrap{
          margin: 30px;
          width: 400px;
          height: 400px;
          border: 1px solid;
          position: relative;
      }

      #inner{
          position: absolute;
          bottom: 10px;
          right: 10px;
          width: 100px;
          height: 100px;
          background: pink;
      }

    </style>
</head>
<body>
    <div id="wrap">
        <div id="inner"></div>
    </div>
</body>
</html>